1. Field of the Invention
The present invention relates generally to vehicle wheels and in particular to a wheel which is drawn, formed and stamped from light metal alloy blanks and a method of manufacturing such a wheel wherein several parts thereof may be formed from a single blank.
2. Description of the Prior Art
Various types of vehicle wheels are well known in the prior art and generally include a center section (sometimes referred to as a spider, flange or web) and a rim section. For example, a common type of automobile wheel is shown in the Ash U.S. Pat. No. 2,551,783 wherein the rim section comprises a pair of separate rim halves each having a drop center and welded together along an annular weld seam at the rim drop center. The center section of the wheel shown in the Ash patent includes an outer, annular flange which is welded to the rim drop center. A disadvantage in constructing such a wheel is that the rim halves are formed from flat strips of metal which are welded together at their ends to form hoop-like bands and thus require additional manufacturing steps.
Alternatively, wheels may be produced from flat blanks by one or a combination of operations including die forming, die stamping, extruding, hot rolling, cold rolling, spinning and drawing. For example, the Parent et al. U.S. Pat. No. 3,222,765 discloses a method of producing a wheel from a flat blank by spinning and die forming operations. However, such methods often result in substantial amounts of waste material when the parts are cut to their final configurations.
Another method of forming wheels from flat blanks is shown in the Albertson et al. U.S. Pat. No. 3,262,191 wherein disk and rim sections having tapered thicknesses are produced in single, continuous power roll forming operations.
Vehicle wheels have also been constructed of various materials, the most common of which are steel and light alloy metals, such as aluminum and magnesium. In view of the current emphasis on minimizing vehicle weight for greater fuel economy, the light alloy wheel constructions are preferred. For example, 14 inch steel automobile wheels weigh approximately 17 pounds each whereas cast aluminum wheels of the same size weigh approximately 13 pounds each and drawn, formed and stamped aluminum wheels according to the present invention weigh approximately 9.5 pounds each.
In addition to their weight advantage with respect to steel wheels, aluminum wheels tend to dissipate brake heat faster and may be polished or brushed to provide an aesthetically pleasing finished appearance which is resistant to rust and corrosion. Steel wheels, on the other hand, must be painted, plated or otherwise protected to prevent rusting. Accordingly, nonplated steel wheels are often provided with hubcaps while aluminum wheels may be designed to exhibit a satisfactory finished appearance without wheel covers, hubcaps and the like.
Furthermore, heat-treated aluminum has a better strength-to-weight ratio than steel. Hence, aluminum wheels are used extensively in high performance applications where strength and weight are crucial, such as for competition racing.
Although cast aluminum wheels are well known and are generally lighter than steel wheels of comparable size, they suffer from several drawbacks. First of all, the molds for casting aluminum wheels tend to be relatively expensive as is the casting process itself. Secondly, substantial amounts of labor are generally required to machine and polish the wheels after casting. Thirdly, it is often difficult to achieve the necessary airtightness in a cast wheel without extensive grinding and polishing or coating with an air-impervious material, all of which add to the cost of such wheels. Finally, in the casting and cooling process the metal alloy may become brittle or fracture.
Thus, light alloy wheels formed in two or more interconnected sections in many respects offer the best available wheel construction for strength, lightness and ease of manufacture. However, heretofore there has not been available either a vehicle wheel or a method of forming a vehicle wheel which combines the advantages and features of the present invention.